This research is longitudinal, depending on data gathered in 1968 for the independent variables and heroin use data to be collected in 1973-74. It is focussed on Puerto Rican adolescents, and is a large scale population, epidemiological study, with over 5,000 subjects involved. The objective of this research program is to 1) obtain a greater understanding and test a set of hypotheses about social, psychological and family factors which are precursors of a person's later use of heroin, 2) develop a statistical model to give predictions of risk of heroin usage for Puerto Rican teenagers, 3) develop a set of instruments to provide the data for the model, and 4) to conduct a set of experiments to find methods of reducing the risk of heroin usage among detected students who have high risk potential. The methods will be a combination of reputational and public document analysis, mailed questionnaire and depth interview. The independent variables will come from a large battery of some 17 instruments originally given to 5,300 junior and senior high school students in 1968. The analysis procedures will be discriminant function and multiple regression for the most part, with some aspects using cannonical correlation and factor analysis. The main hypotheses to be tested are that poor father figures result in rebellious and inadequate feelings of self-worth, which, when associated with a peer group subculture of rebellion which includes use of heroin, will lead to use heroin by the vulnerable young person. It is expected by developing methods of early detection to be able to reduce the likelihood of later heroin addiction by such vulnerable people.